The effects of restraint stress on intake of preferred and nonpreferred solutions in rodents

In these experiments we determined whether stress influenced intake of different flavored test solutions or only those that were preferred. In a series of studies, rats or hamsters were exposed to acute (1 h) or repeated (3 h/day for 3 days) restraint stress immediately followed by access to one of four tastants (saccharin, salt, citric acid, or quinine solutions) paired with water in a 24-h preference test. As rats prefer salt and hamsters do not, both species were used to test the effects of stress on preferred vs. nonpreferred solutions using the same stimulus. Acute restraint inhibited intake of saccharin in rats but had no effect on preference, indicating that suppression of intake was not due to changes in hedonic response. Restraint had no effect on saccharin intake of hamsters but significantly increased salt intake. However, as the preference ratio remained low for the solution (0.26), the stress-induced increase in salt intake was probably associated with a disturbance of sodium and fluid balance rather than a change in sensory perception. This was supported by stress having no effect on intake of nonpreferred solutions in rats or hamsters. Repeated restraint had no effect on salt or saccharin intake of rats when test solutions were presented after stress, but rats showed no preference for saccharin in a subsequent study in which the solution was associated with onset of stress. These results indicate that stress has specific effects on saccharin and salt intake that are not limited to preferred solutions.